1. Field of the Invention
This invention relates to a rotor arm cutting assembly and more particularly to an extensible and retractable rotor arm for a boring-type mining machine.
2. Description of the Prior Art
In boring-type mining machines as illustrated in U.S. Pat. No. 2,890,033 a pair of rotor cutter arms are mounted on a pair of parallel positioned drive shafts that extend forwardly from a gear box at the front of a mining machine. Rotation of the drive shafts rotates the rotor cutter arms to cut a pair of parallel bores in a seam of coal or mineral material to dislodge the material from a mine face. A conveyor mounted on the mining machine conveys the dislodged material rearwardly from the mine face for subsequent conveyance of the material from the mine. Also associated with the rotor cutter arms are cutter bars also mounted on the gear box above and below the rotor cutter arms. The cutter bars include orbitally movable chains that dislodge the cusps depending from the mine roof and upstanding from the mine floor formed by the boring action of the rotor cutter arms.
U.S. Pat. No. 2,937,859 discloses a boring-type mining machine that includes a rotor cutter arm having a base member and a cutter carrier member. The cutter carrier member fits over the base member to telescope relative to the base member. A piston cylinder assembly positioned in the base member is secured at one end to the base member and at the opposite end to the cutter carrier member. Actuation of the piston cylinder assembly shifts the cutter carrier member on the base member from a retracted position to an extended position.
While it has been suggested by the prior art devices to extend and retract the end of a rotor cutter arm, the prior art devices limit the cutting element to the extensible portion of the rotor cutter arm. This limits the cutting action to the end of the rotor cutter arm. Furthermore, by enclosing the piston cylinder assembly within the rotor cutter arm substantial difficulty is encountered in obtaining access to the piston cylinder assembly for maintenance of the assembly or removing the assembly for replacement.
Therefore, there is need to provide for a boring-type mining machine, a rotor arm cutting assembly that is extensible by operation of an actuating device which is readily accessible for repair and replacement on the assembly. There is a further need to maintain an extension portion movable longitudinally on the rotor arm with cutting elements provided on both the fixed portion and the extension portion of the rotor arm.